System for hydrating dates

ABSTRACT

Apparatus and process are disclosed for hydrating dates in order to render them plump and tender. The system of the invention involves first a fissuring of the skin of the fruit, followed by a vacuum hydration operation by which the moisture content of the fruit is rapidly increased without alteration of its natural flavor.

United States Patent Reznik June 26, 1973 SYSTEM FOR HYDRATING DATES[75] Inventor: David Reznlk, Berkeley, Calif. [56] References Cited [73]Assignee: The United States of America as UNITED STATES PATENTSrepresented y the secretary of 1,175,318 3/1916 Stewart 146/237 XAgriculture, Washington, DC. I Przmary ExammerW1llle G. AbercrombleFlled: Feb. 12, Att0rney R [21] Appl. No.: 14,878 57 ABSTRACT RelatedU.S. Application Data 1 Apparatus and process are dlSClOSd for hydratm[62] D' fS N 778165 N 22 1968 P N g 3 dates in order to render themplump and tender. The system of the invention involves first a fissuringof the skin of the fruit, followed by a vacuum hydration oper- {gl (3].ation by which the moisture content of the fruit is rap n n idlyincreased without alteration of its natural flavor.

Field of Search 146/56, 8, 2 367, 296;

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SYSTEM FOR HYDRATING DATES This is a division of my'copendingapplication Ser. No. 778,165, filed Nov. 22, 1968, now US. Pat.No.

A non-exclusive, irrevocable, royalty-free'license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

DESCRIPTION OF THE INVENTION vice.

FIGS. 3 and 4 depict the stem end of a date before and after fissuring.

, It is conventional practice to hydrate dates before packaging them forsale. This is done in order to improve the character of the product. Thedried fruit as it reaches the processor has a low moisture contentwhereby its texture is so tough or hard that it can be eaten only withdifficulty and, if it is to be'cooked, requires a presoak in waterbefore cooking. On the other hand, the hydrated fruit is soft and tenderso that it can be consumed directly. Also, if the product is to becooked, no soaking is needed. The amount of moisture which is added willvary depending on individual choice, trade practices, etc. In general,the moisture content of the hydrated fruit may vary anywhere from about25 to 45 percent.

Various methods have been advocated for accomplishingthe desiredhydration. The conventional methods involve contacting the fruit withboiling water or steam. The treatment is usually conducted at normal'(atmospheric) pressure, but procedures have been advocated wherein thehydration is effected by immersing the dates in water which ismaintained at a temperature above 100 C., using superatmosphericpressure to prevent the water from boiling.

Although hydration procedures using hot water or steam areconventionally used in industry they present certain problems. One isthat the high temperature of the treatments causes at least a partialcooking of the fruit tissue with theresult that flavor changes occur andthe product no longer has the natural taste of the raw fruit. Anotherproblem is that application of the high temperatures causes the datetissue to develop an unnatural rubbery texture. A still further problemis that leaching losses occur-water-insoluble components are dissolvedout of the fruit. These losses are enhanced by the high temperature ofthe treatment and the longprocessing time involved. It is commonpractice to hold the fruit in contact with steam or not water forperiods of l to 8 hours or more to attain the desired uptake of water.

FIG. 2 is a schematic cross-section of the fissuring'de- A particularobject of the invention is the provision of apparatus and processwhereby to obviate the problems outlined above.

The hydration method of the invention has the advantage that it isperformed at ambient (room) temperatures so that the fruit retains itsnatural fresh flavor. There is no development of any cookedflavor as,necessarily occurs when the hydration is done by contact with steam, hotwater, or combinations of steam and hot water. A further advantage ofthe invention is that the product has a desirable soft texture-it iscompletely free from the rubberiness which is common in dates which havebeen hydrated at elevated temperatures. Another advantage of myhydration treatment is its rapidity. The fruit can be fullyrehydrated--for example, its moisture content can be brought to a levelof to 45 percent-in a matter of l to 5 minutes. This is in sharpcontrast with conventional steam or hot water treatments which requirehours to properly hydrate the fruit. Moreover, because my noveltechnique involves a short processing time and low temperature oftreatment, leaching losses are eliminated or at least I greatly reducedbelow those entailed in conventional hydration treatments.

One phase of the invention concerns the procedure used to increase themoisture content of the dates. This involves a vacuum v treatmentconducted, as noted above, at ambient temperature. Another phase of theinvention concerns apparatus and process for pretreatment of the datesto enable them to be effectively hydrated. Basically, this involves afissuring of the skin of the dates. These phases of the invention aredescribed in detail below.

In accordance with the invention, the moisture content of dates isincreased by atreatment which involves the following steps: The datesare placed in a vessel, covered with water, and preferably weighted downwith a perforated ceramic plate or the like to hold them underthe-water. The vessel is then sealed and exhausted by means of aconventional vacuum pump. As the pressure is reduced, air noramllypresent in the date tissue is drawn out. After a'vacuum has beenestablished in the vessel, the operation of the vacuum pump isdiscontinued, and the vacuum is broken,'i.e., air is allowed to enterinto the vessel. As the pressure is so increased, water enters into thedates and occupies the voids in the fruit tissue formerly occupied byair. The moistened dates are then removed from the vessel and are readyfor packaging and distribution. It is obvious that the conditions of thevacuum treatment may be variedto secure a desired uptake of water by thedates. For example, other itemsbeing equal, the application of a higherdegree of vacuum (i.e., lower pressure) will cause a larger increase inthe moisture content of the product. In any particular case the degreeof vacuum required to achieve a desired moisture uptake can be readilydetermined by conducting pilot trials on samples of the dates'to betreated, using different degrees of vacuum and noting which yields aproduct of desired moisture level. This degree of vacuumis then employedin treating the batch of dry fruit to be hydrated.

In conducting the vacuum treatment described above, one may add to thewater any desired preservative such as sulphur dioxide, sodium benzoate,potas sium sorbate, or other conventional water-soluble agent which willprotect the fruit from spoiling in storage. In'a preferred modificationof the invention, one

uses an aqueous solution of potassium sorbate, in a concentration ofabout 0.1 percent. Thereby, the hydrated dates are prevented fromfermentation and spoilage, even if they are stored at high moisturelevels, for example, 30 percent H 06 or above.

As briefly noted above, a second phase of the invention is concernedwith apparatus and process for pretreatment of the dates to enable themto be effectively hydrated. I have observed that some lots of datespresent an impervious surface, that is, the skin is intact and the stemscar is intact. Dates of this kind cannot be hydrated if retained intheir natural condition. Because of their impervious nature, ai'r cannotbe effectively drawn out of the interior tissue nor can water beeffectively introduced into this tissue. However, my investireadilyenter into the meat or inner tissue of the fruit.

The fissuring treatment in accordance with the invention is accomplishedby exerting squeezing forces on the fruit, for example, by passing thembetween rollers. The degree of compression or squeezing is so regulatedthat it is just enough to crack open the skin; it is not so high as tocause any substantial flattening or other permanent deformation of thefruit.

A'preferred form of apparatus for fissuring is shown in FIGS. 1 and 2.This apparatus has the advantage that the distance between the squeezerolls is correlated with the size of the fruit units so that essentiallythe same degree of compression is applied to each fruit unit whether itis large or small. Referring to FIG. 1, the device includes a pair ofsizing rollers 1 the axes of which diverge from one another by a smallangle, and which are rotated by any conventional means (not illustrated)in the directions indicated by the arrows. These rollers are preferablyof smooth metal construction, for example, polished stainless steel.

Beneath sizing rollers l are a pair of compression rollers 2. Thesediverge from one another at the same angle as the sizing rollers, butare spaced closer together. Rollers 2 are rotated by any conventionalmeans (not illustrated) in the directions indicated by the arrows. Theserollers are preferably of metal, grooved lengthwise to grip the datespassing therebetween.

In operation, the dates to be treated are fed onto sizing rollers 1 atthe end where these converge-the left end in FIG. 1. The dates areconveyed by the rollers toward the opposite -end, and this movement isgenerally facilitated by slanting the roller assembly so that thedivergent ends are lower than the convergent ends. As the dates move inthis manner a size sorting occurs in that the smallest ones drop throughthe space between rollers 1 in the area near where the rollers converge,the larger ones drop through further toward the divergent end, and soon. f

Reference is now made to FIG. 2 which is a schematic cross-section ofthe fissuring device. As each date drops through the nip 3 betweenrollers 1 it falls into the corresponding nip 4 between rollers 2. Sincethese latter rollers rotate in an in-drawing manner they pull the datebetween them. Moreover, since nip 4 is smaller than the correspondingnip 3 above it, the date perature.

is subjected to a squeezing action and its skin is fissured. In settingup the apparatus for a run, the position of rollers 2 relative torollers 1 is so adjusted that the dates are subjected to a mildsqueezing action-sufficient to cause development of fissures in the skinbut not sufficient to cause the dates to be substantially flattened orpermanently deformed. The required roller settings may be easilydetermined by pilot trials on a have been so provided with fissures theyare in prime condition for the vacuum hydration procedure.

EXAMPLE The invention is further demonstrated by the followingillustrative example. 1

In these runs, a known weight of fissured dry dates (9 percent moisture)was placed in a vessel, covered with water and weighted to keep thedates under the water. The vessel was sealed and a specified vacuum wasdrawn on the system of dates and water. Thevacuum wasthen released, thedateswere removed from the water, drained, and re-weighed so that thegain in moisture content could be calculated. This procedure was thenrepeated applying different levels of vacuum. The processes in each casewere carried out at room tem- The results are tabulated below.

Vacuum applied,

Having thus described the invention, what is claimed 1. Apparatus forfissuring the skin of dry fruit which comprises, in combination a. afirst pair of rollers arranged with the axes divergent, and rotated sothat their upper surfaces move away from one another, said rollersconstituting means for size sorting fruit units placed thereon, b. asecond pair of rollers mounted beneath said first pair of rollers andarranged with their axes parallel to those of the first pair of rollersbut spaced closer together, the second pair of rollers being rotated insuch direction that their upper surfaces move toward one another, saidrollers constituting means I for receiving size-sorted fruit units whichpass through the first pair of rollers and for exerting compressiveforce on said fruit units,

. the extent of the aforesaid closer spacing being so limited that thefruit units in passing through the second pair of rollers are fissuredbut not otherwise damaged.

wea s:-

1. Apparatus for fissuring the skin of dry fruit which comprises, incombination a. a first pair of rollers arranged with the axes divergent,and rotated so that their upper surfaces move away from one another,said rollers constituting means for size sorting fruit units placedthereon, b. a second pair of rollers mounted beneath said first pair ofrollers and arranged with their axes parallel to those of the first pairof rollers but spaced closer together, the second pair of rollers beingrotated in such direction that their upper surfaces move toward oneanother, said rollers constituting means for receiving size-sorted fruitunits which pass through the first pair of rollers and for exertingcompressive force on said fruit units, c. the extent of the aforesaidcloser spacing being so limited that the fruit units in passing throughthe second pair of rollers are fissured but not otherwise damaged.